Alternating-current relay



Sept. 24, 1929. v

A. F. LAKE ALTERNATING CURRENT RELAY Filed April 6. 1926 l/YVE/VTOE Allan F. bake UNITED STATES mazes PATENT OFFICE ALLAN F. LAKE, OF OAKLAND, CALIFORNIA ALTERNATING-CURRENT RELAY Application filed April 6, 1926.

My invention relates to a relay responsive to failure of current, and particularly to an alarm for indicating failure of alternating current.

Electricity is frequently applied to the automatic and unattended actuation of various devices such as pumps and the like, an unattended stoppage of which would entail serious consequences. It is therefore an object of my invention to announce failure of current, as for example, the current actuating such devices.

Certain inherent difficulties exist in the construction of alternating current relays and it is an object of my invention to overcome these difficulties and provide a device of the character described which is simple, rugged and inexpensive, and which acts only upon failure of the current and which is positive in its action.

It is a further object of my invention to construct a device for the purpose set forth, which may be incorporated at any point in the circuit and requires no special provision for its incorporation.

My invention possesses other objects and features of advantage some of which, with the foregoing, will be set forth in the following description of my invention, which is G illustrated in the drawings forming part of the specification. It is to be understood that I do not limit myself to the showing made by the said description, as i may adopt various forms of my invention within the scope of the claims.

Referring to the drawings Figure 1 is a front elevation partly in section of my relay, with the cover broken away to disclose the mechanism. The coil and associated parts are shown in section.

Figure 2 is a schematic plan of my entire device in one of its applications.

In terms of broad inclusion my device comprises a solenoid coil which may be connected to the source of current for which my device Serial No. 100,022.

constitutes an alarm. The coil is provided with an armature which is normally held in inoperative position by the electro-magnetic flux of the coil. An auxiliary alarm circuit is provided in position to be closed by the armature if and when it is released from its normally inoperative position. Failure of the said current, then, causes a decrease in magnetic flux which permits release of an armature to initiate operation of an alarm.

In terms of greater detail, my invention includes a metal housing 1 of a shape and size suitable to enclose a relay, and provided witha median block 2, of insulating material for supporting the relay. Lugs 3 serve for attaching the housing to any convenient surface, a cover 4: is secured to the housing by screws 6, and openings 7 and 8 provide passages for the leads respectively of the main circuit and an alarm circuit.

The alarm circuit consists of a battery 9, and bell 11, connected to the normally open switch 12, thru leads 13 and 14 to the two binding posts 15 and 16 within the housing.

Wire 17 leads from one binding post to the fixed contact 18 of the switch 12, and wire 19 leads from the other binding post thru a brass spring 20 to the movable contact 21 of the switch. The fixed contact 18 is carried by an L-shaped bar 22 bolted to the bottom of the insulated supporting block 2, and the movable contact is carried by the brass spring 20 which is also bolted to the supporting block. The spring normally hugs the bottom of the supporting block and holds the movable contact above the fixed contact and spaced from it.

Means are provided for closing this normally open switch of the alarm circuit. A threaded hole 23 in the supporting block 2 directly above the movable contact of the switch, exposes the spring 20 to a movable core at of sufficient weight to close the switch 12 against the action of spring 20. A plug 26, of insulating material is pressed into the lower end of this core to insulate it from the switch. The core 24 is housed in a hollow brass cylinder 27 screwed into the hole 23 and thereby supported in vertical position by the block 2. The other end of the cylinder 27 is also threaded and projects up thru a hole in the housing. It is closed by a removable screw cap 28 which permits removal of the core.

The main circuit of the relay provides means for normally retaining the movable core 24 in raised position, where it is inoperative to close the switch of the alarm circuit. VlI'QS 29 and 31 may be connected to the line or source 32, of current the failure of which is to be announced, and lead to binding posts 33, and 34, to which are connected the two ends 36 and 37, of a solenoid coil 38. This coil is supported on the hollow brass cylinder 27 between the supporting block 2 and the top of the housing 1.

The coil is electrically isolated from its surroundings and particularly from the relative ly low voltage alarm circuit, by means of a spool of suitable insulating material. This spool is formed by a hollow bakelite core 39 interposed between the coil 38 and its brass supporting cylinder 27; and annular bakelite disks 41 threaded onto the ends of this brass core 27.

The solenoid coil constitutes an electromagnet and is provided with a fixed iron core piece, or magnet pole, 42 within the hollow brass cylinder 27. This core piece 42 is held at the top of the cylinder 27 by a head 43 at its upper end. The screw cap 28 on the free end of cylinder 27 clamps this head against the top of the cylinder.

The movable core piece 24 is also of magnetic material and constitutes an armature for the electro-magnet, so that when current flows thru the coil, the flux induced will hold this movable core piece or armature up against the fixed core piece or magnet pole 42, and away from the movable contact 21, in which position it is inoperative to close the switch 12. Upon failure of this current however, the flux will decrease to a value insuificient to support the weight of core 24, which will therefore descend against the spring 20, closing the switch 12, to connect the alarm bell with its energizing battery.

Means are provided for minimizing the effect of residual magnetism to insure that the armature 24 will not be held by core piece 42 after current ceases to flow thru the coil. The magnetic resistivity of. the combination is increased by decreasing the area of contact between the cores. For this purpose, the end or face of the movable core 24 is rounded at 44 and drilled at 46 to produce practically line contact between the armature and the pole piece-42 of the electro-magnet.

The current,'the failure of which is to be announced, is illustrated as applied to an alternating current motor 47 driving a centrifugal pump 48, which loses its head when stopped. hen operating on a high suction head, even a momentary interruption of current would incapacitate the apparatus until an operator could be summoned to reprime the pump. It need hardly be mentioned that with such a warning device, the costs of attendance of a pumping station may be materially reduced, while the safety and reliability of the station will be enhanced.

It is contemplated that certain modifications may be made within the broadest concept of my invention. It has been proposed for example, that a spring be inserted between the cores or in other position convenient to permitting operation of my relay in a horizontal position, and that a standard electric plug be added to the free end of wires 29 and 31 to permit removable connection to any standard electric light socket in the line. It has also been proposed that various other forms of switch be substituted for the switch herein illustrated, and that various other methods of increasing the magnetic resistivity of the movable core relative to its weight, be resorted to. However, for the present application the illustrated forms comprise a most desirable combination and are preferred for their simplicity, ruggedness and universality, and it is considered that, having taught the fundamental ideas, the modifications suggested are within the scope of this invention.

I claim:

1. An electromagnetic switch comprising an electro-magnethaving a core, a vertically movable armature for the magnet normally held in raised position by the magnetic flux, a normally open switch below the armature, said armature being operative when released, to close ,said switch, and means comprising a hollow-ended pole on one of said magnetic members for decreasing the effect of residual magnetism.

2. An electromagnetic switch comprising an insulating disk having an aperture therein, a coil mounted on one side of said disk, 21 fixed core in said coil, a movable armature in said coil and projecting thru said aperture, a movable switch contact mounted on the other ,side of the disk and lying below the aperture, a cooperating fixed switch contact, and means comprising a hollow ended pole on one of said magnetic members for decreasing the effect of residual magnetism. I

3. An electromagnetic switch comprising an electro-magnet having a core, a vertically movable armature for the magnet normally held in raised position by the magnetic flux, a normally open switch below the armature, said armature being operative when released, to close said switch, and means comprising poles on said magnetic members shaped to provide substantially a line contact therebe- 15 my hand. 7

ALLAN F. LAKE. 

